The structure, according to University of Tennessee paleobiology professor Colin Sumrall, was a 475-millon-year-old fossil belonging to an extinct sea creature known as a trilobite.

"Typically when we look at fossils of trilobites, they molt when they grow,” Sumrall told ABC affiliate WATE.com. “So what happens is, when the trilobite skeleton just crumbles into hundreds of little pieces. To find one where all the pieces are intact, it's actually a pretty lucky find.”